Hydraulic system for reducing mills and the like



e. B. coE 3,112,561 HYDRAULIC SYSTEM FOR REDUCING MILLS AND THE LIKEDec. 3, 1963 2 Sheets-Sheet 1 Filed March 28, 1961 INVENTOR.

GEORGE B. COE

Ill/Ill!!! ZN, slimfiw iz Dec. 3, 1963 G. B. coE 3,112,661

HYDRAULIC SYSTEM FOR REDUCING MILLS AND THE LIKE Filed March 28, 1961 2Sheets-Sheet 2 FIG. 2

IN V EN TOR.

' G EORGE B. CO E ATTORNEYS United States Patent 3,112,661 7 I HYDRAULICSYSTEM FOR REDUCING MHLS AND THE LIKE George B. Coe, Westfield, N.J.,assignor to Tube Reducing Corporation, a corporation of Delaware FiledMar. 28, 1%1, Ser. No. 98,834 8 Claims. 01. 80-14) This inventionrelates to fluid driving systems for stock reducing machines and similarmills and, more particularly, to a closed hydraulic system adapted tooperate the stock manipulating means of such mills.

Reducing machines of the type with which this invention is especiallyconcerned are mills in which metal stock, in the form of either tubes orrods, is advanced intermittently into reciprocating dies which reduceits diameter in successive longitudinal increments. A full descriptionof such a reducing machine is set forth in my United States LettersPatent No. 2,954,126. The reducing dies generally comprise a pair ofopposed cylindrical rolls, each having a tapered circumferential grooveformed therein, and are mounted one over the other in a reciprocablesaddle such that the tapered grooves are in direct opposition. The stockis advanced into the opposed grooves and, as the dies reciprocate withthe saddle, the stock is reduced within the converging walls of thetapered grooves. At the end of each forward working stroke of the dies,the stock is given an incremental turn about its axis, perhaps aquarter-turn, so that when the dies roll back over the stock anyundesired fins or the like in the worked portion may be faired out. Uponreturning to starting position, the stock is fed forward a longitudinalincrement so that an additional portion thereof is brought into theworking zone, and the finished reduced stock advances out of the dies atthe outlet side thereof. If tubular stock is being reduced, a taperedmandrel is usually located within its bore at the working zone betweenthe dies to support and size the inside surface of the tube. Ordinarily,the mandrel is mounted on a rearwardly extending rod and is turned alongwith the stock at the end of each working stroke of the dies.

(To carry out these feeding and turning steps at the proper time duringthe cycle of operation, two turning devices and one feeding device areusually included in a tube reducing machine. The two turning devices are(1) an assembly at the inlet end of the machine which engages both thestock and the mandrel rod (if any) and which can turn both elementsabout their common longitudinal axis, and (2) an assembly at the outletend of the machine which grips the emerging reduced stock to turn it inunison with the first-mentioned assembly at the inlet end of themachine. By these means, the stock can always be turned even when itstrailing end is entering the dies. The stock feeding mechanism comprisesa longitudinally movable non-rotatable screw shaft which may be advancedintermittently by a rotatable non-translata-ble feed-nut assembly. Theforward end of this screw shaft urges the stock gripping assembly (i.e.,that part of the first-mentioned turning device which holds the stock)forwardly by increments as the feed-nut assembly is intermittentlyturned.

Heretofore, the most successful means for operating these feeding andturning devices was a hydraulic system which was actuated by a timer camdriven in synchroniza-. tion with the reciprocating saddle in which thedies are mounted. In general, this known hydraulic system is as follows:A fluid motor is provided to drive each of the inlet turning device, theoutlet turning device, "and the feeding device. To send fluid underpressure through these motors at the proper moment to effect theirdesired intermittent operation, three respective cylinder and pistonassemblies are provided and are operated by a common 3,112,661 PatentedDec. 3, 1963 rotating timer cam synchronized to make one revolution ateach complete stroke of the saddle. Each cylinder and piston assemblyintermittently displaces a certain volume of fluid to its associatedfluid motor to operate the motor at the desired time. The fluiddischarge from each motor is directed into a reservoir which suppliesthe pistons with additional fluid during each non-working return strokethereof.

One of the greatest difiiculties in driving precisely timed machinery.by fluid motor systems of this sort is to insure that the motors stoptheir operation at exactly the right moment. In an attempt to achievethis in the system described above, it has been proposed to include abrake valve in the outlet or discharge conduit of each fluid motor tohalt the flow of drving fluid and cease the motors operation at theprecise time desired. Absent such-brake valves, the momentum of themotors and their driven parts causes over-travel which is in no wayprevented by the fluid surging into the open reservoir. However, thefluid valves which prevent over-travel also act as accumulators andbuild up considerable backpressure in the system. The cylinder and pumpassemblies must work against this back pressure, of course, and theactuation by the timer cam is made just that much more diflicult. As aresult, considerably more power must be put into the hydraulic systemthan is actually used for effective work. This factor of inefliciencyalone is a serious disadvantage, but the problem is worsened by thegreat amount of heat energy which develops in the hydraulic system.Furthermore, and this is perhap'sthe most serious defect of theconventional hydraulic system, the speed of the machine is definitelylimited by the feed and turn driving system. Because of highback-pressure, the extra actuating force necessarily developed by thetimer cam, and the increased temperature of the system,the conventionaltube reducingmachines cannot be operated above a certain speed withoutadversely aifecting the timing of the stock fee'd and turn mechanisms.Obviously, this imposes a definite limit on the productive output ofeach mill.

The present invention constitutes an improvement over reducing machinesof the type described in my aforementioned Letters Patent, namely thosehaving reciproca-ble dies and at least one stock moving (e.g., feedingor turning or both) (device. Broadly stated, the invention provides aclosed fluid driving system for such a device comprising a fluid motorhaving inlet and outlet ports. Variable capacity fluid pumping andreceiving chambers are provided in communication respectively with theseinlet and outlet ports. A conduit interconnects the chambers. Means areincluded for maintaining unidirectional flow from the pumping chamberthrough the motor to the receiving chamber and thence through theconduit back to the pumping chamber. Means are also'provided formaintaining this system completely filled with operating fluid.Actuating means are included for contracting the pumping chamber andexpanding the receiving chamber an equal amount to operate the motorWithout over-travel thereof and then contracting the receiving chamberand expanding the pumping chamber. an equal amount to return the systemto starting position without operating the motor. 1

It is apparent that this new fluid driving system is closed as opposedto the conventional open system described hereinbefore. In the oldsystem, fluid is pumped through the motors and into an open reservoironly after pumping pressure exceeds the maximum accumulatedback-pressure established by the brake valves. The reservoir, which isnever subjected to pump pressure, is. definitely part of the fluidcircuit. In the new system,

however, fluid travels from each pump to the associated,

motor and back to the pump in a closed circuit, and the reservoir'isemployed only to dispense added fluid into thesystem when needed tocompensate for leakage. Overtravel of each fluid motor is prevented withmaximum eliectiveness because the receiving chamber downstream of the.motor accepts discharge fluid only to the extent that operating fluid ispumped into the motor from the pumping chamber. Hence, as the pumpingchamber contracts. to operate the motor, the receiving chamber expandstoaccept the discharge fluid. Assoon as the pumping action stops, so too.does the acceptance of'the discharge fluid in the receiving chamber, andthe operation of the motor is thereby cut off immediately. Under theseconditions, over-travel of the motor is virtually impossible.

Another important feature of the new system is that the pumps whichoperate the motors do not act against any significant back-pressure.There are no accumulators or brake valves or the like at any point inthe line. As the. pump piston moves forward, it displaces. fluid onlyagainst the force of fluid friction and the resistance of the motoritself, becausev back-pressure is eliminated by the expanding receivingchamber.

Since. there is no appreciable back-pressure created in the. systemprovided by this invention, there is practically no heat given. off bythe fluid even after prolonged operation of the machine. Moreimportantly, the absence of back-pressure permits the pistons to moveback and forth at whatever speed is. desired, and still the fluid motorsdriven thereby start and stopat precisely the predetermined times. Nolonger is the output of the reducing mill limited bythe. operation ofthe feeding and turning devices. It isnow possible to run the machine atthehighest rate. at which thesaddle can be reciprocated.

A preferred embodiment of the. invention is described hereinbelow: withreference to the accompanying drawings, wherein.

FIG; 1 is a schematic illustration of one form of the new fluid systemin conjunction with the basic elements of a. tube reducing machine; and.

BIG; 2.is' a si'milarillustration of. another form. of the new; system.Referring to bothFIGS. l and'2, a sufficient number ofthe basic elementsof a tube reducing machine are shown for purposes of understanding thepresent invention. They-are describedat the same time with reference tothe embodiments of both figures, though the reference nu merals, areprimed in FIG. 2 for purposes of. distinction. For a full and completediscussion of'the overall structure and function of atube reducingmachine, reference may be had tomy aforementioned Letters Patent. A pairof dies are mounted in a saddle 11 which is. adapted to bereciprocatedback and-fortl so that the dies roll against one another. Both dies havetaperedv groovesformed'in their-circumference, which grooves. togetherdefine a die orifice. A. length of tubular stock 12 isinserted betweenthe dies within the groovesthereof and a tapered-'- mandrel 13:supported by a mandrel rod 14. extends within the stock to theworkingzone between the dies 10; As the dies. rollback and forth, they; reduceboth the inside and outside diameter of the stock 12 against the mandrel13' to form asmooth finished tube12A which advances from; the exitend ofthe machine.

At' the end of each forward stroke of' the saddle and dies: (in theposition thereof shown in both FIGS. 1 and- 2 the stock 12 is turnedatboth the inlet and outlet endsof the machine; For this purpose, thestock 1 2- is held at itsv trailing end by a releasable chuck 16 and-atits forward end by. a gripper. 17; Thechuck 16 is rotatably mounted andcan be turned by agear train 18 drivenfrom a; shaft 1 9 Which, in turn,can be intermittently rotated by a fluid motor 20; Likewise, the gripper17' is. rotatably mounted and can be -turned by a gear- 21 drivenNotonly is the stock 12 turned at the inlet end ofthe machine butthemandrel 13is turned withit'. To achieve 4. this, the shaft 19 extendsrearwardly to a gear train 23 which can rotate the rear end of themandrel rod 14' rotatably mounted in a mandrel rod carriage 25. Duringoperation of the machine, the carriage 25 is held locked by a suitablelatch 26 to prevent any longitudinal displacement of the mandrel. 13. s

By these means, a partial turn is imparted to the stock and mandrel.(e.g.,. av quarter-turn) by a brief periodic actuation of the turningmotors 20 and 22. With turning means on both sides of the saddle anddies, there is always assurance that a portion of the stock. will begripped and turned even though its trailing end may be entering thedies. By imparting a slight turn to the stock at each stroke of thedies, successively different circumferential portions of the stock arepresented to. the working surfaces of the dies, so that any ovalityorthe like which: may be formed during the previous working stroke areflattened out.

At the end of each return stroke of the saddle and dies, the stock isadvanced a predetermined longitudinal increment to move successiveunworked portions thereof into the working zone between the dies. Forthis pur pose, the stock gripping chuck 16 is' not only rotatablymounted but is also longitudinally displaceable on a suitable carriagewhich can be moved by the forward end ofa feed screw 27. The feed screw27 is non-rotatable, but can be. longitudinally displaced to move thechuck 16 either forwardly or rearwardly. The. means for displacingthefeed screw 27 comprises. a feed-nut 28in threaded;engagementtherewith which is rotatably mounted but is non-translatable.A fluid motor 29 is provided to rotate the feed-nut 28 in eitherdirection to advance or retract the feed screw 27 and the stock 12.There is, of course, suitable structure.- to permit the feed screw 27to. advance the chuck 16. and the stock 12 atthe same time the shaft 19intermittently turns the chuck 16. Such structure forms no part; of thepresent invention and is described fully inmy aforementioned. patent.

By these means, it is possible to advance. the stock 12 over the.mandrel 13 each time the dies 10 and'saddle 11 complete. their returnstroke. Ordinarily, the 1011: gitudinal distance covered by. the. stock12. in each increment: of feed is rather slight but must be quiteprecise inorder to; achieve a uniform working action within the dies.

Further auxiliary means are shown in both FIGS. 1, and: 2L by which thetube reducingv machine may be; returned. to its starting positionpreparatory tothe reduc tion of a new tube. As soon as the trailing end?of the previouslength of stock 12 nears the dies 10, the saddle 11 isstopped for a brief period. The operator then. runs the feed motor 29 atrelatively high speed in a reverse direction to withdraw the chuck 16rapidly to the rear, i.e., to the left as seen in the figures. Also, theoperator releases. the latch to free the carriage 25 and then withdrawsthe, mandrel 13 from the Working zone bymoving the mandrel rod carriageZS reMWardIy. Thus, a. latch-actuator 31' is hydraulically operated towithdraw. the latch 26 and release the carriage 25. The carriageZS ismounted'on suitable longitudinal ways and is adapted. to. be displacedtherealong by. an endless chain 32 mounted on sprockets 33. A mandrelpull-- back fluid motor 34v is provided: to drive this chain 32in eitherdirection sothat the carriage 35 may be displaced reanwardly orforwardly asv desired; After the operator has withdrawn the mandrel 13from the dies (by operatingthe latchfactuator 31 and the'pull-back motor34), a. new. length of stock is. placed inthe machine and gripped by.the chuck 16. The mandrelipull-back mov tor 34' isthen actuated again toreturn the. mandrel into: the dies, and: the carriage 35 is. locked bythe actuator:

31. The new stock is then advanced until it; abutsthe trailing end ofthe partly reduced stock within the dies,- and the tube reducing machinecontinues in its: operation.

Hence, there are five hydraulic driving meanswhich must be actuated toinsure the desired operation of the tube reducing machine. The turningmotors and 22 are to operate intermittently While the saddle and diesreciprocate back and forth. The feeding motor 29 must be capable ofsimilar intermittent operation, but must also be reversible at highspeed when it is desired to insert a new length of stock into themachine. Finally, the mandrel pull-back motor 34 and the latch-actuator31 are selectively operated only when new stock is put into the machine.

It is the purpose of the invention to provide a new and improved fluidsystem for driving these various hydraulic means.

Referring first to the embodiment shown in FIG. 1, a timing mechmsm 35is provided which is substantially the same as that described in myLetters Patent No. 2,594,126. Hence, it includes a cam 36 mounted on acountershaft 37 which is driven directly by the main driving means whichreciprocates the saddle 11 of the tube reducing machine. The directmechanical connection between the saddle drive and the countershaft 37is such that the countershaft 37 makes one complete revolution upon eachback and forth reciprocation of the saddle 11. The cam 37 is adapted toreciprocate a slide 38 back and forth so as to displace two primarydrive rods 39 and 40. The drive rod 4% is adapted to actuate adouble-acting piston 41 movable within a cylinder 42 and also to actuatea. double-acting piston 43 movable within a cylinder 44.

The cylinder 42 operates the stock and mandrel tuming motor 29 at theinlet end of the machine. On one side of the piston 41, a pumpingchamber 45 is defined and on the other side thereof a fluid receivingchamber 46 is provided. The fluid motor Zfl includes an inlet portwhichis connected with the pumping chamber 45 by an inlet conduit 47 and anoutlet port connected to the receiving chamber 46 by an outlet conduit49. The pumping and receiving chamber 45 and 46 are connected by aconduit 50. To maintain this system completely filled with operatingfluid, afeed conduit 51 leading to the conduit is in communication witha gravity feed reservoir 52. In order to provide proper unidirectionalflowin the system (from the pumping chamber 45 to the motor 29, then tothe receiving chamber 46, and finally back to the pumping chamber 45), acheck valve 53 is provided in the outlet conduit 49, a check valve 54 isprovided in the conduit 50 and a check valve 55 is provided in thesupply conduit 51.

The piston 43 and cylinder 44, with which the primary rod 45 is alsoassociated, are adapted :to operate the stock turning motor 22 at theoutlet end of the machine. Again, the double-acting piston 43 defines apumping chamber 57 and a receiving chamber 58. The former is connectedby an inlet conduit 59 to an inlet port of the fluid motor 22, and theoutlet port of the fluid motor 22 is connected by an outlet conduit 60with the receiving chamber 58. interconnecting the pumping and receivingchambers is a conduit 61, and a feed conduit 62 leads from the reservoir52 to the bypass conduit 61. Check valves 64 in the outlet conduit, 65in the conduit Gland 66 in the supply conduit insure the properunidirectional flow in the system, which is from the pumping chamber tothe motor to the re ceiving chamber and back to the pumping chamber.

The turning motors 2t and 22 are operated as follows: The cam 36 isconfigured such that it drives the rod 40 to the right as seen in FIG. 1each time the saddle 11 reaches the forward end of its stroke. Thus thepiston 41 moves to the right, forcing fluid through the inlet conduit 47and causing the motor 29 to turn and thus rotate the mandrel 13 and thestock 12 at the inlet end of the machine. There is little back-pressurebecause discharge fluid from the motor 20 is simultaneously forcedthrough the outlet conduit 49 and into the expanding receiving chamber46. Back-flow through the cham- V 6 ber 50 during this pumping stroke ofthe piston 41 is prevented by the check valve 54. As soon as the pumping stroke of the piston 41 stops, the motor 20 also stops without anyover-travel because the receiving chamber 46 no longer expands andthere. is no space available for any further surge of fluid from thedischarge port of the motor. Thus, the motor freezes and precise turningof the stock and mandrel is achieved. During'the return stroke of thesaddle 11, the cam 3-6 causes the piston 41 to move to the left toreturn to its starting position. As this happens, back-flow through theoutlet conduit 49 is preventedby the check valve 54 and the excess fluidin the receiving chamber -46 is forced into the pumping chamber 45through the conduit 50. Any leakage of fluid from the system iscompensated for upon demand rom the reservoir through the feed conduit51 and the check valve 55. J

The motor 22 operates in exactly the same manner. The piston 43 moves inprecise unison with the piston 41 to force fluid through the inletconduit 59 and thereby rive the motor 22 without encounteringappreciable back-pressure. Over-travel is likewise prevented since thereceiving chamber 58 allows only a controlled discharge from the motor22. Again, the return stroke of the piston 43 causes displacement offluid from the receiving chamber 58 to the pumping chamber 57 throughthe conduit 61. 1 V

Returning now to the timing mechanism 35, its other primary rod 39drives another double-acting piston 68 which operates Within a cylinder69. The mechanical linkage therebetween includes a rocker arm 71 havingan adjustable fulcrum 72 as described in my aforementioned patent. Thepiston 68 and cylinder 69 are adapted to operate the stock feeding motor29, and thus apumping chamber 73 is connected by an inlet conduit 74 tothe inlet port of the motor 29 and an outlet conduit 75 extends from theoutlet port of the motor to a receiving chamber 76. An auxiliary system77 for high speed reverse operation of the motor 24 describedhereinbelow is not in operation when the motor29 is driven incrementally in a forward direction. A conduit 80 interconnects the pumpingandreceiving chambers 73 and 76 and a a supply conduit 81 leads from thereservoir 52. Unidirectional flow is maintained by check valves 82 inthe outlet conduit, 83 in the conduit 80, and 84 in the sup; plyconduit. v I

The cam 36 is configured such that upon completion of each return strokeof the saddle 11, the piston 68 moves to the right to force fluidthrough the inlet conduit 74'to drive the motor 28 and thereby cause thestock to be fed forward a short distance. Back-pressure. and over-travelare both eliminated by-the controlled ex pansion of the receivingchamber 76 which receives the discharge fluid. Thereafter, the cam 36causes the piston 68 to return to the left thus displacing fluid throughthe conduit 80 without aifecting the motor 29. A 2-way valve 78 isprovided to divert fluid from the pumping chamber 73 to the reservoir 52to interruptthestock feeding action when desired.

At those intervals when a new length of stock is placed in the machine,it is necessary to withdraw the chuck 16 and this is done by theauxiliary system 77 which is. i1 lustrated diagrammatically by a slidevalve 85. In the solid line position of the valve 8 5, two bores 86 and87 register with the inlet and outlet conduits 74 and 75 of the motor 29so that the motor operates in a forward direction as described abovewhen the saddle 11 is reciproeating. However, when the saddle is stoppedand the valve 85 is moved to the right, the movable bores 86 87 registerwith a pump inlet conduit 89-89A and a pump outlet conduit 9090A. Fluidis forced through the inlet pump conduit 89-89A from a pump 92 by anauxi iliary motor 93. Hence, fluid is forced through the motor 29 in adirection reverse to that described previously and the dicharge flowsback through the pump outlet conduit 90-90A and into the reservoir 52.From the reservoir, the fluid enters the pump 92 on demand through afeed conduit 95. This particular auxiliary system exemplifies means fordriving the motor 29 in a reverse direction when desired.

Means are also included for operating the latch-actuator 31 and themandrel pull-back motor 34. These include. a pump 97 supplied through afeed conduit 98 from the. reservoir 52 and driven by the motor 93 topump. fluid. through a main inlet conduit 99 which branches into twosecondary inlet conduits 100 and 161. The former passes through a 4-wayvalve 102 to. power the. latch-actuator 31 andthe discharge therefromreturns through the 4-way valve 102 to an inletconduit103 which leads,back to the reservoir 52. The other secondary inlet conduit 101 extendsto another 4-Way valve 105 from which fluid can proceed to the mandrelpull-back motor 3.4 and. thence back through the 4-way valve 105 to thecommon. outlet conduit 103. Selective operation of the latchfactuator 31and. themandrel pull-back motor 34 is made possible by changing thevalves 102 and 105 from their. positionwhere they simply circulate thepumped fluidfrom they inlet conduit 99 immediately back through thereturn conduit 103 to by-pass the motor 34 and ac tuator 31..

Turning now to the embodiment of FIG. 2, a timing mechanism 107 is shownwhich is identical to that described. in the previous embodiment. Itoperates a main fluid driving. system: for the stock. and mandrelturning motor the stock turning motor 22., and the stock feeding motor29. This is done here by means of singleacting pistons andv cylinders,whereas in the previous em? hodiment. double-acting pistons andcylinders were em{ ployed. Thus, the. stock and mandrel turning motor20" at the inlet end of the machine is driven by a pumping chamber 1.08.in a. single-acting piston and cylinder assembly 109 and a receivingchamber 110 in another. single-acting pistonand cylinder assembly 111.As. is clear from.FIG-. 2, these pumping. and receiving chambers are invassociation with suitable conduits and. check valves throughouh, suchthat the motor 20 can be driven. incrementally asin. the previousembodiment. However, it. is important. to note thatthe timing mechanism.107 drives the assembly 109 from aprimary rod 115 and the assem-.- bly110'. fromv a primary rod. 116. Both of these. rods have exactly thesame stroke so that as one movesin the.

other moves outandthedisplacement within-the pumping and receiving.chambers 108 and 110. isv equal.

Likewise, thestock turning motor 22? at. theoutlet end of the. machine.is. incrementally turned by a single-acting pumpandcylinder assembly118. having a pumping chamber 119 and. a single-acting pump cylinderassembly 120 having a receiving chamber 121. Suitableconduits areassociated therewith as. above, along with the necessary check valvestoprovide unidirectional flow. The assemhlies 1'18 and.120 aresynchronized in the same manner The; stock feeding motor 29' is.alsodriven in the same a manner as in the previous embodiment exceptthat here.

two; single-acting; piston and cylinder assemblies 124 and 125 areemployed. rather than one double-acting assembly.. Thus, pumping and.receiving chambers 126 and 127 respectively workin unison to turn themotor 29intermittently. The necessary. conduits and. check valves areincluded asshown.

'An auxiliary system including a valve 130, auxiliary 7 pumps 131 and132,1two 4-way valves. 133 and 134 and the required conduits thereforare provided for the selec tive periodic operation of the latch-actuator31', the mandrel pull-back motor 34', and the high speed reverse Allthis is exactly receiving chamber and finally back to the pumpingchamher. All this is done with no substantial back-pressure resistingthe expansion and contraction of the pumping. and receiving chambers.More importantly, it. is impossible for the associated motors toover-travel because in the closed system all fluid motion ceases whenthe pistons in the pumping and receiving chambers stop theirdisplacement. Hence, each motor travels to the extent desired While thepumping chamber contracts and the receiving chamber accepts thedischarge fluid; but once the pumping chamber stops contracting and thereceiving chamber likewise stops expanding, the incompressible fluid inthe line prevents the associated motor from running any further. Thisprevention of over-travel allows the greatest precision in the degree inwhich the stock is fed and turned during the reducing process. Sincethere is no practical limit to the rate of oscillation of a closedsystem of the type provided herein, the production output of a machineembodying the invention is limited only by the speed at which the saddlecan be reciprocated.

I claim:

1. In a mill for reducing stock including reciprocable dies and at leastone stock moving device, a closed fluid driving system for said devicecomprising a fluid motor having inlet and outlet ports, variablecapacity fluid pumping and receiving chambers in communicationrespectively with said inlet and outlet ports, a conduit interconnectingsaid chambers, means for maintaining unidirectional flow from saidpumping chamber through said motor to said receiving chamber andthencethrough said conduit back to said pumping chamber, means formaintaining. said system completely filled with operating fluid, andactuating means for contracting said pumping. chamber and expanding.said receiving chamber an equalamount to operate said motor withoutover-travel thereof and. then contracting said receiving chamber and'expand-v ing said pumping chamber an equal amount to return the systemto starting position without operating said motor. 2. Apparatusaccording to claim 1 wherein said means for maintaining said systemcompletely filled with operating fluid comprises a reservoir, afeed'conduit extending from said reservoir to said closed system, and acheck valve in said feed conduit for maintaining unidirectionalflow'from said reservoir to said closed system.

3..Apparatus according to'claim. 1 wherein said fluid:

V pumping and receiving chambers are provided by two respective separatesingle-acting cylinder and piston assemblies;

4. Apparatus according to claim 1 which includes a double-actingcylinder and piston assembly wherein one side defines said pumpingchamber and the other side defines said receiving chamber. 7 V

51 In amill for reducing tubular stock including; re

ciprocable" dies, a rotatable mandrel, a feeding device forintermittently advancing said stock, and a turning device forintermittently turning said mandrel and stock; a closed fluid drivingsystem for operating each of said devices comprising a fluid motor. foreach device having inlet and outlet ports, fluid pumping and receivingpiston chambers in communication respectively With said inlet and outletports, a conduit interconnecting said chambers, check'valve means formaintaining unidirectional intermittent flow fromsaid pumping chamberthrough said motor to said receiving chamber and thence through saidconduit back to said pumping chamber, means for maintaining said systemcompletely filled with operating fluid, and

actuating means synchronized with said reciprocable dies for advancingand withdrawing the pistons of said pumping and receiving chambersrespectively through an equal displacement to operate said motor withoutover-travel thereof and then Withdrawing and advancing said respectivepistons through an equal displacement to return the system to startingposition Without operating said motor.

6, In a mill for reducing tubular stock including reciprocable dies, arotatable mandrel, a feeding device for intermittently advancing saidstock, a first turning device on the inlet side of said dies forintermittently turning said mandrel and stock, and a second turningdevice on the outlet side or" said dies for intermittently turning thereduced stock; a closed fluid driving system for operating each of saiddevices comprising a fluid motor for each device having inlet and outletports, fluid pumping and receiving piston chambers in communicationrespectively With said inlet and outlet ports, a conduit interconnectingsaid pumping and receiving chambers, check valve means for maintainingunidirectional intermittent flow 20 from said pumping chamber throughsaid motor to said receiving chamber and thence through said conduitback to said pumping chamber, a reservoir, a gravity feed conduitextending from said reservoir to said by-pass conduit, a check valve insaid feed conduit for maintain- 25 ing unidirectional flow from saidreservoir to said conduit, and actuating means synchronized with saidreciprocable dies for advancing and withdrawing the pistons of saidpumping and receiving chambers respectively through an equaldisplacement to operate said motor Without over-travel thereof and thenwithdrawing and advancing said respective pistons through an equaldisplacement to return the system to starting position without operatingsaid motor.

7. Apparatus acording to claim 6 wherein said fluid pumping andreceiving piston chambers are provided by two respective separatesingle-acting cylinder and piston assemblies.

8. Apparatus according to claim 6 wherein said fluid pumping andreceiving piston chambers are provided by one double-acting cylinder andpiston chamber wherein one side defines said pumping chamber and theother side defines said receiving chamber.

References Cited in the file of this patent UNITED STATES PATENTS 65,435Richter June 4, 1867 2,594,126 Coe Apr. 22, 1952 2,932,223 ChartrandApr. 12, 1960

1. IN A MILL FOR REDUCING STOCK INCLUDING RECIPROCABLE DIES AND AT LEASTONE STOCK MOVING DEVICE, A CLOSED FLUID DRIVING SYSTEM FOR SAID DEVICECOMPRISING A FLUID MOTOR HAVING INLET AND OUTLET PORTS, VARIABLECAPACITY FLUID PUMPING AND RECEIVING CHAMBERS IN COMMUNICATIONRESPECTIVELY WITH SAID INLET AND OUTLET PORTS, A CONDUIT INTERCONNECTINGSAID CHAMBERS, MEANS FOR MAINTAINING UNIDIRECTIONAL FLOW FROM SAIDPUMPING CHAMBER THROUGH SAID MOTOR TO SAID RECEIVING CHAMBER AND THENCETHROUGH SAID CONDUIT BACK TO SAID PUMPING CHAMBER, MEANS FOR MAINTAININGSAID SYSTEM COMPLETELY FILLED WITH OPERATING FLUID, AND ACTUATING MEANSFOR CONTRACTING SAID PUMPING CHAMBER AND EXPANDING SAID RECEIVINGCHAMBER AN EQUAL AMOUNT TO OPERATE SAID MOTOR WITHOUT OVER-TRAVELTHEREOF AND THEN CONTRACTING SAID RECEIVING CHAMBER AND EXPAND-K INGSAID PUMPING CHAMBER AN EQUAL AMOUNT TO RETURN THE SYSTEM TO STARTINGPOSITION WITHOUT OPERATING SAID MOTOR.